Poly-gamma-glutamate having ultra high molecular weight and method for using the same

ABSTRACT

The present invention relates to a poly-gamma-glutamate (PGA) having an ultra-high molecular weight greater than 5,000 kDa. The ultra-high molecular weight PGA according to the present invention has a mean molecular weight greater than 13,000 kDa, and more than 95% of its molecules have a molecular weight ranging from 3,000 to 15,000 kDa. Also, it can be produced by the culturing of  Bacillus subtilis  var. chungkookjang. The ultra-high molecular weight PGA according to the present invention shows very excellent moisture-absorbing, moisture-retaining, sustained release, mineral solubility, and water-absorbing properties, and thus, can be used as a new and high value-added material in various applications.

FIELD OF THE INVENTION

The present invention relates to an ultra-high molecular weightpoly-gamma-glutamate (hereinafter, referred to as “PGA”) produced by ahalotolerant strain Bacillus subtilis var. chungkookjang (KTCT 0697BP)isolated from chungkookjang, Korean traditional fermented soybean food,and also to the method of use thereof. More particularly, the presentinvention relates to a PGA with a molecular weight greater than 5,000kDa showing edibility, water solubility, an anionic property andbiodegradability, and also to foods, cosmetics, feedstuffs, mineralabsorption-promoting compositions, which contain the same.

BACKGROUND ART

PGA is a viscous polymer where D,L-glutamate is polymerized troughgamma-glutamyl. It is produced from a Bacillus sp. strain, which isisolated from chungkookjang as Korean traditional food obtained from thefermentation of soybeans using ricestraw, natto as Japanese traditionalfermented soybean food, and kinema as Nepalese traditional fermentedsoybean food.

The PGA produced from the Bacillus sp. strain is a polymer havingedibility, water solubility, an anionic property and biodegradability,and can be used as a raw material of moisture-absorbing agents,moisture-retaining agents and cosmetics, and a raw material for thepreparation of naturally degradable plastics using the synthesis ofester derivatives.

Recently, with respect to the production and use of the PGA, there arebeing actively conducted studies on the development of a material as asubstitute for difficultly degradable polymers, and the production ofheat-resistant plastics by esterication, and the production ofwater-soluble fibers and membranes, etc., in highly developed countriesas a leader. Furthermore, studies on a change in physical properties ofthe PGA occurring upon irradiation of the PGA with gamma rays, andstudies on the development and industrial application of a PGA hydrogelusing crosslinkers.

The PGA hydrogel is an environment-friendly material, which is producedby the intermolecular or intramolecular crosslinking of the PGA, abiopolymer produced by the culturing of Bacillus subtilis varchungkookjang, and has a water-absorbing property, biodegradability andthermoplasticity. Methods for the crosslinking of the PGA includeirradiation with radiation, such as gamma rays or electron beams,treatment with chemical crosslinkers, such as epoxy resin, and the like.When aqueous PGA solution is irradiated with radiation, the crosslinkingbetween PGA molecules takes place, thereby giving PGA resin having awater-absorbing property, biodegradability and thermoplasticity.

In the prior art, there were reported a study on an effect of manganeseions on the composition and production of PGA, a study on the productionof the PGA having water solubility by ultrasonic decomposition, and astudy on the production of plastics of low water solubility by synthesiswith ester derivatives (Biosci. Biotechnol. Biochem., 60(8):1239-42,1996), a study on the production of PGA using Bacillus subtilis, and astudy on the use of the PGA for healthy foods having a therapeuticeffect of osteoporosis, such as a calcium-dissolving agent, etc.(Japanese patent laid-open publication No. Heisei 6-32742).

In addition, there was reported an effect of PGA on the reduction ofwater contamination according to the reduction of a phosphorus contentin a water system (European patent No. 838160). Moreover, highlygelling, water-soluble, biodegradable and adsorbent PGA resins, and theuse thereof for sanitary products and foods and in horticulturalindustries, etc., were disclosed (Japanese patent laid-open publicationNos. Heisei 10-251402, 7-300522 and 6-322358).

Furthermore, there were known the use of PGA for solid biodegradablefibers, films or film-shaped materials by the dissolution, precipitationand drying of the PGA (Japanese patent laid-open publication Nos. Heisei7-138364 and 5-117388), and the use of the PGA for a drug carrier(Japanese patent laid-open publication Nos. Heisei 6-92870 and6-256220).

Meanwhile, there were known inventions on the efficient production ofthe PGA (Korean patent application No. 1997-67605), the production ofhigh concentration PGA (Korean patent application No. 2001-0106025), andhalotolerantstrain Bacillus subtilis var. chungkookjang of producing ahigh-molecular weight PGA (PCT application No. PCT/KR01/01372corresponding to Korean patent laid-open publication No. 2001-78440).

The molecular weight of PGAs produced in the prior art is in the rangeof about 100-2,000 kDa, and they have limitations on the applicationthereof, particularly in cosmetic or food fields, in terms of thesolubility, absorption and sustained release of minerals.

Accordingly, the present inventors have conducted extensive studies inan attempt to produce an ultra-high molecular weight PGA, andconsequently, found that the batch culturing of Bacillus subtilis var.chungkookjang in medium containing glucose, citric acid and glutamateyielded a PGA having a molecular weight greater than 5,000 kDa withoutbyproducts, and the produced PGA showed a very excellent effect upon theuse thereof for moisture-retaining agents, water-absorbing agents, andmineral absorption-promoting agents. On the basis of this point, thepresent invention was perfected.

DISCLOSURE OF INVENTION

Therefore, a main object of the present invention is to provide a PGAhaving an ultra-high molecular weight greater than 5,000 kDa.

Another object of the present invention is to provide cosmetics, foodsand feedstuffs containing the ultra-high molecular weight PGA.

Still another object of the present invention is to provide a hydrogelproduced from the ultra-high molecular weight PGA, as well as amoisture-absorbing or water-absorbing agent containing the same.

Yet another object of the present invention is to provide a mineralabsorption-promoting composition, which contains the ultra-highmolecular weight PGA and a mineral.

To achieve the objects as described above, the present inventionprovides an ultra-high molecular weight PGA having a mean molecularweight greater than 5,000 kDa.

Preferably, the molecular weight of the PGA according to the presentinvention is in the range of 5,000 to 15,000 kDa.

Since the PGA according to the present invention has ultra-highmolecular weight, it has very excellent moisture-absorbing andmoisture-retaining properties as compared to the prior PGA withrelatively low molecular weight. Thus, the present invention alsoprovides foods, cosmetics and feedstuffs containing the ultra-highmolecular weight PGA.

A hydrogel produced from the PGA of the present invention as a rawmaterial has a very excellent water-absorbing property as compared tothe prior product with relatively low molecular weight. Thus, thepresent invention also provides a hydrogel produced from the ultra-highmolecular weight PGA, as well as a moisture-absorbing or water-absorbingagent containing the same.

The PGA according to the present invention has a very excellent propertyof enhancing the solubility of mineral ions, and an excellent propertyon the sustained release of mineral ions. Thus, the present inventionalso provides a mineral absorption-promoting composition, which containsthe ultra-high molecular weight PGA and a mineral.

In the present invention, the mineral is preferably Ca, Fe, Mg, Zn, Cuor Se, but minerals essential for a living body may also be used withoutspecial limitation.

In the present invention, the PGA may also be substituted with acopolymer of a PGA having an ultra-high molecular weight greater than5,000 kDa and a polyamino acid bearing a positive charge. The polyaminoacid is preferably polylysine or polyarginine. The PGA according to thepresent invention bears a negative charge, and thus, canelectrostatically bind to the polyamino acid to form a copolymer.

Furthermore, the present invention provides a method for using theultra-high molecular weight PGA with a molecular weight greater than5,000 kDa, for a mineral absorption-promoting agent

In the present invention, the ultra-high molecular weight PGA isproduced by microbial culturing. A microorganism used for the productionof the ultra-high molecular weight PGA in the present invention isBacillus subtilis var. chungkookjang (KCTC 0697BP) whose isolation,identification and physiological characteristics are described in detailin PCT application No. PCT/KR01/01372, which was filed in the name ofthe present inventors on Aug. 11, 2001.

The morphological and physiological characteristics of this strain areas follows.

This strain is gram-positive bacteria, which form milky colonies uponculturing on an LB agar plate, and show active growth in aerobicconditions above 37° C. and slow growth at a culturing temperaturehigher than 55° C. Furthermore, this strain is a halotolerant stain thatcan grow even at a salt (NaCl) concentration of 9.0%, which is higherthan the salt tolerance of general Bacillus subtilis species. Also, itis a typical Bacillus strain, which forms endospores when it is culturedin LB liquid medium or solid medium for at least 70 hours. Thecomparative analysis of the 16S rDNA sequence of this strain and the 16SrDNA sequence of the prior Bacillus sp. strain reveals that this strainhas a very high homology of 99.0% with Bacillus subtilis.

BRIEF DESCRIPTION OF DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a graph showing the molecular weight distribution of the PGAaccording to the present invention;

FIG. 2 is a graph showing the comparison between the water-absorbingproperty of the ultra-high molecular weight PGA of the present inventionand a product of the prior art;

FIG. 3 is a graph showing the comparison between the moisture-retainingproperty of the ultra-high molecular weight PGA of the present inventionand a product of the prior art;

FIG. 4 is a graph showing an effect of the ultra-high molecular weightPGA according to the present invention on the improvement of Casolubility;

FIG. 5 shows a change in intestinal Ca absorption according to time,when PGA with a 5,000-kDa molecular weight of the present invention isused; and

FIG. 6 is a graph showing an effect on water absorption of a hydrogelproduced from the ultra-high molecular weight PGA of the presentinvention as a raw material.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will hereinafter be described in further detail byexamples. It should however be borne in mind that these examples aregiven for illustrative purpose only and the scope of the presentinvention is not limited to or by the examples.

Although the production of the ultra-high molecular weight PGA usingBacillus subtilis var. chungkookjang (KCTC 0697BP) was illustrated inthe examples, it is to be understood that a PGA produced by otherstrains or chemical methods falls within the technical scope of thepresent invention as long as it is an ultra-high molecular weight PGAwith a molecular weight greater than 5,000 kDa.

EXAMPLE 1 Production and Molecular Weight Measurement of Ultra-HighMolecular Weight PGA

In order to examine if the production of ultra-high molecular weight PGAis made possible through the optimization medium and culturingconditions, the following test was carried out.

A 5L fermenter containing 3L minimal medium (GS medium containing 4%L-glutamate, 3% glucose, 1% (NH₄)₂SO₄, 1% Na-citrate, 0.27% KH₂PO₄,0.42% Na₂HPO₄, 0.05% NaCl, 0.3% MgSO₄, 1 ml/L vitamin solution, pH 6.8)was inoculated with 1% of a culture broth of Bacillus subtilis varchungkookjang KCTC 0697BP), and cultured at a sting of 150 rpm, anaeration rate of 1 vvm, and 37° C. for 3 days, and then adjusted to pH3.0 by the addition of 2N sulfuric acid solution, thereby obtaining aPGA-containing sample solution.

The sample solution was left to stand at 4° C. for 10 hours to removepolysaccharides present in the fermented solution, and added withethanol at the amount of two times volume larger than the fermentedsolution, and then nixed thoroughly. The mixed solution was left tostand at 4° C. for 10 hours, followed by centrifugation, to give a PGAprecipitate.

The precipitate was dissolved by the addition of distilled water, addedwith 100 μg/ml protease, and allowed to react in a 37° C. incubator,thereby decomposing extracellular protein present in the PGA sample.

The resulting substance was dialyzed against a sufficient amount ofdistilled water to remove free glutamate, followed by concentration, togive pure PGA.

As shown in FIG. 1, it could be found by GPC analysis that the meanmolecular weight of the PGA obtained as described above is 13,000 kDa,and more than 95% of its molecules have a molecular weight ranging from3,000 to 15,000 kDa.

In this case, the molecular weight of the PGA was measured by gelpermeation chromatography (GPC). For the molecular weight analysis ofPGA using GPC, a GPC system (Youngin Scientific Co, Ltd, Korea) equippedwith two GMPW_(XL) columns (VISCOTEK Co.) was used. As a solvent, 0.1NNaNO₃ was used at a flow rate of 0.8 ml/minute. Polyethylene oxide wasused as the standard for the GPC analysis, and a refractometer (VISTOTEKCo.) was used to measure the molecular weight of the PGA.

The molecular weight of a prior PGA obtained by the culturing ofBacillus subtilis var. chungkookjang (KCTC 0697BP) was about 2,000 kDa(Korean patent laid-open publication No. 2001-78440), but in the presentinvention, the ultra-high molecular weight PGA with a molecular weightgreater than 5,000 kDa could be successfully produced through theoptimization medium and culturing conditions.

EXAMPLE 2 Moisture-Absorbing and Moisture-Retaining Properties ofUltra-High Molecular Weight PGA

The moisture-absorbing and moisture-retaining properties of theultra-high molecular weight PGA produced in Example 1 were compared toan existing PGA having a molecular weight of 600 kDa

-   (1) Comparison of Moisture-Absorbing Property

0.5 g of each of the PGA obtained in Example 1 and a prior product witha molecular weight of 600 kDa were put in the respective Petri dish andmaintained in a 45° C. incubator for 14 hours to remove watercompletely. The resulting samples put in a decicator (relative humidity:81-88%) containing a saturated aqueous solution of calcium carbonate(250 g calcium carbonate per 500 g purified water), and were measuredfor a change in its weight according to time (moisture-absorbingproperty) for 24 hours. The measured results are shown in FIG. 2.

As shown in FIG. 2, it was found that the PGA with a 600 kDa molecularweight showed less than 10% increase in water content after 24 hours,whereas the PGA according to the present invention showed about 60%increase in water content, indicating an extraordinarily excellentmoisture-absorbing property of the inventive PGA.

-   (2) Comparison of Moisture-Retaining Property

Samples, which had been sufficiently moisturized by standing for 48hours under the conditions described in the above test (1), were put ina decicator (18% humidity) containing 500 g dry silica gel and measuredfor a reduction in its water content according to time(moisture-retaining property) for 24 hours at 25° C. The measuredresults are given in FIG. 3.

As shown in FIG. 3, it was found that the prior PGA with a 600 kDamolecular weight showed 13% reduction in its water content after 24hours, whereas the ultra-high molecular weight PGA of the presentinvention showed about 10% reduction in its water content, demonstratinga very excellent moisture-retaining property of the inventive PGA.

From the results of this example, it can be found that the ultra-highmolecular weight PGA of the present invention can be used for a varietyof moisture-retaining and/or moisture-absorbing products, such ascosmetics, foods, feedstuffs etc.

Example 3 Ca Solubility of the Ultra-High Molecular Weight PGA

In order to examine the Ca solubility of the ultra-high molecular weightPGA of the present invention, the following test was carried out.

The ultra-high molecular weight PGA produced in Example 1 was diluted toprepare PGA solutions having concentrations of 0.062, 0.125, 0.25 and0.5 mg/ml, respectively. 0.5 ml of each of the PGA solutions was addedto a reaction solution containing 0.5 ml of 10 mM CaCl₂ and 1.0 ml of 20mM phosphate buffer, followed by reaction at 37° C. After 2 hours, therespective solutions were centrifuged at 2000 g for 30 minutes, and Caremaining in the supernatant was quantified with a Ca quantification kit(Wako Chemical Co., Japan). In addition, as control groups, a marker A(PGA commercially available from Ajinomoto Co., Japan), a PGA with amolecular weight of 1,000 kDa and a PGA with a molecular weight of 2,000kDa were tested for their Ca solubility. The test results are shown inFIG. 4.

As shown in FIG. 4, the inventive PGA dissolved (adsorbed) Ca ions at asignificantly larger amount than the prior products over all theconcentrations. Particularly, at a PGA concentration of 0.125 mg/ml, themarker A, the 1,000-kDa molecular weight PGA and the 2,000-kDa molecularweight PGA showed Ca solubility of about 12%, 27% and 37%, respectively,whereas the ultra-high molecular weight PGA with a 5,000-kDa molecularweight showed a Ca solubility of about 46%.

Example 4 Intestinal Ca Absorption-Promoting Effect of Ultra-HighMolecular Weight PGA

The ultra-high molecular weight PGA produced in Example 1 was tested forits effect of promoting intestinal Ca absorption.

The PGA with a molecular weight of 5,000 kDa was diluted to preparesolutions having concentrations of 0.05, 0.1 and 0.2%, respectively, andmixed with 5 mM calcium chloride. 1 ml of each of the solutions wasadministered orally to mice. In order to prove that the ultra-highmolecular weight PGA has an excellent effect of promoting intestinal Caabsorption, a comparative test of the inventive PGA and a 1,000-kDamolecular weight PGA was also carried out.

Thirty 4-week-old male BALB/c mice were purchased, housed in a mousecage under a 12:12-hour dark-light cycle at suitable temperature, andfed with basal feedstuffs and distilled water. The mice were dividedinto three groups each consisting of 10 animals. The first group wasadministered with the PGA having a 1,000-kDa molecular weight, thesecond group was administered with the PGA having a 5,000-kDa molecularweight, and the third group was a control group to which no PGA wasadministered. The PGA solution sample containing calcium chloride wasadministered orally to the respective groups, and phosphate buffersolution was administered to the control group.

At 2 hours after oral administration, the animals were anesthetized withether, and the entire small intestines ranging from the duodenum to theileum were detached from the abdomen of the mice. The small intestineswere divided into two portions of an upper portion and a lower portion,and then washed with cold saline water. Next, the small intestinetissues were homogenized by a homogenizer with the addition of coldsaline water. The homogenized tissues were centrifuged at 8,000 rpm and4° C. for 20 minutes. After centrifugation, a soluble fraction and aninsoluble precipitate in the respective tissue samples were collectedand stored at −20° C. while analyzing their Ca content with aquantification kit (Wako Chemical Co., Japan). The results of theanalysis are given in Table 1 below.

As shown in Table 1, it could be found that the ultra-high molecularweight PGA with a molecular weight of 5,000 kDa showed an excellenteffect of promoting Ca absorption. This suggests that the ultrahighmolecular weight PGA can be used for industrial or edible products forCa absorption. TABLE 11 Effect of promotion of Ca absorption accordingto molecular weight of PGA (Ca content: mg) PGA concentration Upperportion Lower portion (%) 5,000 kDa 1,000 kDa 5,000 kDa 1,000 kDa 00.132 0.070 0.131 0.072 0.05 0.147 0.075 0.134 0.074 0.1 0.154 0.0820.138 0.073 0.2 0.167 0.090 0.140 0.072

Example 5 Effect of Ultra-High Molecular Weight on Sustained Release ofCa Ions in Intestines

In order to examine if the inventive PGA with a molecular weight of5,000 kDa has an effect on the sustained release of Ca ions inintestines, the following test was carried out.

A solution of 0.2% PGA with a molecular weight of 5,000 kDa was mixedwith 5 mM calcium chloride, and 1.0 ml of the solution was administeredorally to mice. Thereafter, the mice were subjected to the sameprocedure as in Example 4, except that the mice were anesthetized withether at 1, 1.5 and 2 after the oral administration of the PGA solution,and then, the entire small intestines ranging from the duodenum to theileum were detached from the abdomen of the mice. The test results areshown in FIG. 5.

As shown in FIG. 5, the administration of the mixed solution, whichcontains the inventive PGA having a molecular weight of 5,000 kDa andthe calcium chloride, indicated that intestinal Ca absorption rate wasincreased with the passage of time. This suggests that the PGA accordingto the present invention has an excellent effect on the sustainedrelease of a mineral in the intestines.

Example 6 Effect of Use of Ultra-High Molecular Weight PGA on Promotionof Absorption of Fe Ions into Blood

In order to examine if the use of the inventive PGA with a 5,000-kDamolecular weight has an effect on the promotion of absorption of Fe ionsinto blood, the following test was conducted.

A solution of 0.04% PGA with a 5,000-kDa molecular weight was mixed with20 mM ferrous lactate, and 1.0 ml of the solution was administeredorally to mice. In order to prove that the ultra-high molecular weightPGA has an excellent effect on the promotion of absorption of Fe ions, acomparative test of the inventive PGA and a 1,000-kDa molecular weightPGA was also carried out.

Thirty 4-week-old male BALB/c mice were purchased, housed in a mousecage under a 12:12-hour light dark cycle at suitable temperature, andfed with basal feedstuffs and distilled water. The mice were dividedinto three groups each consisting of 10 animals. The first group wasadministered with the PGA with a 1,000-kDa molecular weight, the secondgroup was administered with the PGA with a 5,000-kDa molecular weight,and the third group was a control group to which no PGA wasadministered. The solutions containing the PGA and calcium chloride wereadministered orally to the respective groups, and the control group wasadministered with phosphate buffer solution.

At 3 days after oral administration, the animals were anesthetized withether, and blood was taken from the animals and measured for its Fecontent with a particle counter model PCE-170 (ERMA Inc., Japan). Themeasured Fe content was also expressed in terms of the amount ofhemoglobin. The measured results are given in Table 2 below.

As evident from Table 2, it could be found that the administration ofthe inventive PGA having a 5,000-kDa molecular weight had a veryexcellent effect on the promotion of Fe absorption into blood. Thissuggests that the ultra-high molecular weight PGA of the presentinvention can be used for industrial or edible products for Feabsorption. TABLE 2 Effect of promotion of Fe absorption according tomolecular weight of PGA Hemoglobin content Fe content No. Group (g/100ml) (mg/100 ml) 1 Control group 12.8-13.1 11.1 2 PGA (MW: 1,000 kDa)14.2-15.3 11.9 3 PGA (MW: 5,000 kDa) 14.7-17.0 12.8

Example 7 Water-Absorbing Property of Ultra-High Molecular Weight PGAHydrogel

5% aqueous solution of each of the ultra-high molecular weight PGAproduced in Example 1 and a prior PGA product (600 kDa) was irradiatedwith gamma ray of 25 kGy, thereby producing hydrogels.

Then, each of the produced hydrogels was immersed in water, and after 24hours, measured for its weight in water, thereby examining awater-absorbing property of the hydrogels. The measured results areshown in FIG. 6.

As shown in FIG. 6, the prior PGA hydrogel absorbed 2000 times itsweight in water, but the inventive PGA hydrogel absorbed 6400 times itsweight in water, that indicates 3 times higher water absorptioncapability than that of the hydrogel containing the prior PGA product.As a result, it can be found that water-absorbing hydrogel produced fromthe inventive PGA shows an excellent effect of absorbing an increasedamount of water even at a lower volume than hydrogel produced from theprior PGA.

INDUSTRIAL APPLICABILITY

As described above, the present invention provides the ultra-highmolecular weight PGA having a molecular weight greater than 5,000 kDa.Furthermore, the present invention provides cosmetics, feedstuffs andfoods containing the ultra-high molecular weight PGA, as well as highlywater-absorbable hydrogel produced from the ultra-high molecular weightPGA. In addition, the present invention provides the mineralabsorption-promoting composition, which contains the ultra-highmolecular weight PGA having a molecular weight greater than 5,000 kDaand thus significantly increases the absorption of a mineral into thebody. Since the PGA according to the present invention has ultra-highmolecular weight, it has very excellent effects on the absorption of amineral into the body and on the sustained release of a mineral in thebody, and thus, can be used for industrial or edible products formineral absorption.

1. An ultra-high molecular weight poly-gamma-glutamate (PGA) having amean molecular weight of at least 5,000 kDa.
 2. The PGA according toclaim 1, which has a mean molecular weight ranging from 5,000 to 15,000kDa.
 3. The PGA according to claim 1, which is produced by Bacillussubtilis var. chungkookjang (KCTC 0697BP).
 4. A hydrogel produced fromthe PGA according to any one of claims 1 to
 3. 5. Cosmetics containingthe PGA according to any one of claims 1 to
 3. 6. Foods containing thePGA according to any one of claims 1 to
 3. 7. Feedstuffs containing thePGA according to any one of claims 1 to
 3. 8. A water-absorbing agentcontaining the hydrogel according to claim
 4. 9. A mineralabsorption-promoting composition, which contains the PGA according toany one of claims 1 to 3, and a mineral.
 10. The mineralabsorption-promoting composition according to claim 9, which has asustained release property.
 11. The mineral absorption-promotingcomposition according to claim 9, wherein the mineral is Ca, Fe, Mg, Cuor Se.
 12. The mineral absorption-promoting composition according toclaim 9, wherein the PGA is substituted with a copolymer of anultra-high molecular weight PGA having a mean molecular weight of atleast 5,000 kDa and a polyamino acid bearing a positive charge.
 13. Themineral absorption-promoting composition according to claim 12, whereinthe polyamino acid is polylysine or polyarginine.
 14. A method for usingthe PGA according to any one of claims 1 to 3 for a mineralabsorption-promoting agent.